Command Explanations

--prefix=$(pkg-config --variable=prefix
ORBit-2.0): Setting the prefix using this parameter
instead of with $GNOME_PREFIX will
ensure that the prefix is consistent with the installation
environment and the package will be installed in the correct
location.

--sysconfdir=/etc/gnome/2.18.3: This
parameter causes the configuration files to be installed in
/etc/gnome/2.18.3 instead of
$GNOME_PREFIX/etc. Additionally (if
applicable), the parameter ensures that the GConf-2 database is correctly updated.

--localstatedir=/var/lib:
This parameter is used so that all ScrollKeeper files are installed in, and the
ScrollKeeper database is properly
updated in /var/lib/scrollkeeper
instead of some files being installed in $GNOME_PREFIX/var/scrollkeeper.

--mandir=$(pkg-config --variable=prefix
ORBit-2.0)/share/man: This parameter causes the
man.(X) files to be installed in
$GNOME_PREFIX/share/man/man(X)
instead of $GNOME_PREFIX/man/man(X).